Means for desensitizing carbonless papers

ABSTRACT

THE DISCLOSED DESENTIZING AGENTS, WHEN COMBINED WITH A SUITABLE SOLVENT, CAN BE USED TO DENSITIZE &#34;CARBONLESS&#34; PAPERS OF THE DTO/METAL TYPE WHEREIN THE DTO (DITHIOOXAMIDE) COMPOUND IS ENCAPSULATED AND IS RELEASED FOR CHEMICAL INTERACTION WITH A COREACTANT METAL SALT BY RUPTURE OF THE CAPSULES. THE PREFERRED DENSITIZING AGENTS ARE PARTIAL ESTERS OF ETHYLENEDIAMINETETRAACETIC ACID, WHICH PARTIAL ESTERS ARE SOLUBLE IN SUITABLE ORGANIC MEDIA AND FORM STABLE, SUBSTANTIALLY COLORLESS COMPLEXES WITH, FOR EXAMPLE, NICKEL SALTS. VARIOUS HOMOLOGS AND ANALOGS OF THESE PRTIAL ESTER DERIVATIVES ARE ALSO OPERATIVE IN THE INVENTION, AS ARE CERTAIN LESS PREFERRED COMPOUNDS, I.R. CERTAIN DIAMINES, OXIMES, AND VIC-DIMERCAPTANS. THE PREFERRED DENSITIZING AGENTS ARE ALSO USEFUL FOR DESENTIZING &#34;CARBONLESS&#34; PAPERS OF THE LEUCO DYE/ACIDIC CLAY TAPE.

D. R. YARIAN 3,809,668

MEANS FOR DESENSITIZING CARBONLESS PAPERS v May 7, 1974 Filed Jan.

u u a a o e 5 e c n o u, u o

Int. Cl. C08g 51/26; C08h'17/26; C09k 3/00 U.S. Cl. 260-33.4 UR 8 ClaimsABSTRACT OF THE DISCLOSURE The disclosed desensitizing agents, whencombined with a suitable solvent, can be used to desensitize carbonlesspapers of the DTO/metal type wherein the DTO (dithiooxamide) compound isencapsulated and is released for chemical interaction with a coreactantmetal salt by rupture of the capsules. The preferred desensitizingagents are partial esters of ethylenediaminetetraacetic acid, whichpartial esters are soluble in suitable organic'media and form stable,substantially colorless complexes with, for example, nickel salts.Various homologs and analogs of these partial ester derivatives are alsooperative in the invention, as are certain less preferred compounds,i.e. certain diamines, oximes, and vic.dimercaptans. The preferreddensitizing agents are also useful for desensitizing carbonless papersof the leuco dye/ acidic clay tape.

This invention relates to a means and method for desensitizing thepressure-activated interaction of imageforming reactants and coreactantsand to paper sheets densensitized by this means. The invention is usefulin the art of carbonless paper; that is, sheets of paper which formimages corresponding to a pattern of pressure applied to their sufaces.See, for example U.S. Pat. 2,548,366 (Green et al), issued April 1951.Typically, carbonless paper takes the form of a manifold copy sheetwhere individual sheets in the manifold are treated or coated, on atleast one surface, with a material which reacts with a dye precursor orcolor-forming reactant. An aspect of this invention relates to a meansand method for desensitizing or blocking out a portion of thecolorreactive coating or treated area. A further aspect of thisinvention relates to a means and method for treating the entire surfaceof a self-contained self-imaging paper [see Example 18 of U.S. Pat.3,516,846 (Maston) issued June 1970] to preserve and render tamper-proofimages already formed thereon, i.e. so that further pressure applied tothe surface will not activate the image-forming reaction. The inventionis particularly useful with carbonless systems in which the dyeprecursor is dithiooxamide (DTO) or DTO derivatives. Preferredembodiments of the invention are also useful in systems wherein the dyeprecursor is an electron donor material such as benzoyl leuco methyleneblue, or similar leuco dyes or Michlers hydrol (see, for example, theGreen et al., patent cited previously) The carbonless paper described inthe aforementioned Green et al. patent makes use of a color reactionwherein the leuco dye (electron donor), which is encapsulated, isreleased upon rupture of the capsules to react with an acidic silicateor clay or the like (electron acceptor), which is coated on the copysheet. According to U.S. Pat. 2,777,780 (Cormack et al.), issued January1957, portions of the electron acceptor coating can be desensitized withcationic quaternary ammonium salts, higher aliphatic or aryl amineacetates, high molecular weight primary amines and primary diamines suchas dodecyl amine or dodecyl diamine, or substituted oxazolines. All thespecific chemical compounds taught by Cormack et al. to be desensitizershave limited utility. These compound Were chosen specically todeactivate the clay (or United 'States Patent O 3,809,668 Patented May7, 1974 other electron acceptor) in a leuco dye/ clay reaction, and areinoperative or unsuitable for deactivating one or more of the reactantsin a system using a DTO-type dye precursor and a salt of a metal such asnickel, copper, cobalt, or cadmium. Furthermore, several of thedesensitizers disclosed by Cormack et al. are ammonium salts and thusare too polar for use in typical printing ink compositions.

Thus, until this invention, a chemical means for desensitizingcarbonless paper based on DTO/metal-salt chemistry was not available.Physical means, of course, have been developed for all carbonless papersystems, including the DTO/metal salt type. One physical system involvesthe masking of the image areas with a non-contrasting background such asdark blue, black, or purple. The colored image is simplyindistinguishable from, or indiscernible because of, the background. Anobvious disadvantage of this non-contrasting background method is thatthe background indiscriminately masks any intelligence entered in thebackground area, be it by pressure activation of the DTO/metal-saltreaction, or by pencil or pen. The industry much prefers a selectivemethod which blocks out only the images obtained by thepressureactivated chemical interaction (i.e. capsule rupture) but notordinary ink or pencil entries. Still another physical method is toprovide a physical barrier between the dye precursor and the coreactantsalts, eg. with a varnish overcoat on top of the metal salt coating.Reliable quality control has proved to be extremely diicult to obtainwith this method. Over a period of Weeks or months, the DTO-typecompound may penetrate through the varnish barrier to the metal saltbeneath and form an image. Thus, the thickness of the varnish barrier iscritical and involves careful adjustments of coating thickness that areinconvenient and impractical for commercial printing practice.

Many of the theoretically possible chemical means for desensitizing theDTO/ metal-salt reaction have proved to be ineifective. For example, itshould be theoretically possible to provide coatings containing metalsalts (c g. zinc salts) which would scavenge the DTO-type compound byforming colorless complexes. However, the reaction of, for example,nickel soaps with DTO or D-BDTO, or N,N bis(2 octanoyloxy ethyl)dithiooxamide (DOEDTO), or other commonly used DTO/metal-salt reactions,are so highly favored that the zinc is an ineffective competitor anddoes not deactivate all the DTO, DBDTO, DOEDTO, etc. Similarly, poorlycontrolled results are obtained by overcoating the copy sheet withcoatings of aluminum soaps, i.e. on top of the nickel-containingcoreactive coating. Overcoating with various salts or soaps of chromium,cadmium, manganese, lead, iron, cobalt, tin, and copper also failed toachieve reliable and controllable desensitizing of the DTO/'Ni reaction.In general, attempts to tie up DTO or its derivatives with a competingmetal ion are no more eifective and no more subject to quality controlthan the physical barrier method discussed previously. (DBDTO isdi-benzyl-DTO, i.e. N,Nbis(benzyl)dithiooxamide).

Theoretically, it should also be possible to provide a means fordeactivating or tying up the metal salt coreactant rather than theDTO-compound. However, several problems are inherent in this approach.First, the typical image reactions (e.g. DBDTO/m'ckel soap) are stronglyfavored. Even if the coreactant metal ions (e.g. Ni, Co, or Cu ions)were tied up in a fairly stable, colorless or low-contrast coloredchemical complex, it is quite possible that the DTOtype compound couldliberate the ions from the non-contrasting complex and form or re-formthe highly colored DTO/metal-salt complex (DTO/Ni, DTO/Cu, DTO/Co,etc.). Second, a complexng agent for the coreactant metal ion would haveto be compatible with standard ink compositionsv used in letterpress,rubberplate, dry offset, and other printing methods using inkscontaining oily liquid carriers. Preferably, the complexing agent shouldalso be sol-uble in the more highly volatile carriers used inflexographic inks. To restate this requirement, the complexing agentshould be soluble in a variety of ink vehicles and/or plasticizers ofvarying viscosity and volatility used in the various printing processes.Third, the action of the complexing agent should not be significantlyinterfered with by drying agents such as the cobalt salts used withstandard drying oils. Fourth, the complexing agent should preferably benon-toxic and dermatologically inactive. |Fifth, if the complexing agentis chemically modified to make it more compatible with oil, thischemical modification should be of a type which will not swell or deformrubber rollers in an inking train. Sixth, the complexing agent shouldreact with the coreactant metal ion (e.g. Ni, Cu, Co, etc. ion) to forma stable, lowcontrast complex, preferably a complex which is white,colorless, or very light in color, or a complex having a color whichstrongly contrasts with brown, black, purple, and other colors producedby DTO/metal-salt complexes. For example, if the complexing agentreacted with a nickel salt to produce a purple compound, the use of acomplexing agent would not have significant advantages over the printedblock-out system described previously. Seventh, the complexing agentshould be suitable for use with the self-contained type of carbonlesspaper disclosed in 'Example 18 of the Matson patent, previously cited.That is, it should be possible to render this type of carbonless paperinsensitive to pressure by applying the complexing agent or desensitizerafter intelligence has been entered on the sheet. Eighth, and perhapsmost important, coreactant metal salts (esg. Ni soaps) Iwill not readilyreact with a desensitizer except in the presence of a solvent(hereinafter referred to as a cosolvent) capable of dissolving both thedesensitizing or complexing compound and the `metal salt. Manyconventional ink vehicles will not dissolve these metal salts.

The requirements relating to the different types of printing methods arevery specific and can be conflicting. Thus, as pointed out previously,flexographic printing normally involves an ink vehicle of highvolatility, while letterpress and similar methods involve low volatilityinks. However, in any of these printing methods, the ink must containthe aforementioned cosolvent and must also have good penetrating power,so as to penetrate the full depth of the nickel coating on the copysheet, and preferably should be incapable of adversely affecting r-ubberrollers due to solvolytic or swelling action or other chemical orphysical effects of this type.

The prior art relating generally to the complexing of nickel, copper,and cobalt ions, and other color-reactive heavy metal or transitionmetal ions, is not particularly helpful. An extremely wide variety ofcomplexing compounds or ligands are known to be capable of tying up ionsof the transition metals, but many of these would be unsuitable for usein the present invention. One problem is that many of these ligands formrelatively weak or unstable complexes with transition metal ions. Thechemical literature does contain data relating to the stability of,inter alia, coordination compounds of metals and various ligands orchelating agents, but these data were generally derived from studies inaqueous media. Needless to say, the most Widely used large-run printingsystems do not employ water-based inks, but rather inks which employorganic vehicles of varying ldegrees of polarity, as well as volatilityand viscosity. Some metal chelating agents such asethylenediaminetetraacetic acid (EDTA) and derivatives thereof have beenused as scavengers or stabilizers for various metal salts, and asplasticizers, in organic systems. Thus, amine salts of EDTA-typecompounds have been used as stabilizers for the lead tetraethyl inleaded 4 lgasoline. 'See U.S. Pat. 2,901,335 (Fields et al.), issuedAugust 1959. EDTA has been reacted with a tdialkanol amine and a fattyacid to provide an emulsifier useful in oily or oil-in-water rustproofing compositions. See U.S. Pat. 2,794,000 (Ruedrich), issued May1957. Esters of EDTA have been suggested for use as plasticizers, e.g.in making tire stocks. See U.S. Pat. 2,428,353 (Bersworth), issuedOctober 1947. Amides of EDTA have been used to remove metal ioncontaminants from monomers and polymers, the amide form being used toprovide hydrocarbon solubility. See U.S. Pat. 3,234,173 (Mann et al),issued February 1966. INone of these disclosures regarding the use ofEDTA or its derivatives in organic systems is any clue whatever towhether the solubility requirements of various printing ink systems canbe met and whether the chelating agents are as effective in organicmedia as they are in aqueous media. In fact, preliminary studiespreparatory to this invention indicate that amides of EDTA and higheralkyl amines are almost insoluble in ester-type cosolvents (solvents forboth the coreactant metal ion and the chelating agent), e.g. tributylphosphate. Thus, the prior art relating to chelating agents generallyhas given yno attention to, much less provided guidelines for, means forrendering typical chelating agents compatible with both inrk vehiclesand cosolvents for coreactant metal salts or soaps.

Accordingly, this invention contemplates, for 4desensitizingcolor-forming reactions, a desensitizing compound at least partiallysoluble in a cosolvent for coreactant metal salts (partic-ularly soapsof nickel, cobalt, or copper) which forms a chemical complex -which ismore stable than the DTO/ nickel (or DTO/Co or DTO/ Cu) complex inorganic media, which is compatible with various ink vehicles, and whichforms a white, colorless, or other lowcontrast material. 'Ihis inventionalso contemplates the use, in printing carbonless paper, of variousmetal chelating agen-ts which are compatible with cosolvents for themetal salts, wherein the cosolvents have widely varying volatility andpolarity and viscosity characteristics, depending on the type ofprinting system to be used. This invention also contemplates carbonlesspaper desensitizers comprising chelating agents which are substantiallynon-toxic and do not cause contact dermatitis, and which are preferablynon-hygroscopic. Among the printing methods contemplated for use with-this invention are letterpress, rubberplate, dry offset, lithographieand flexographic. Among the ink vehicles contemplated for use with thisinvention `are the usual oleaginous type and alcohols or the like ofrelatively high volatility. The use of estertype plasticizers in inks ofthis invention is also contemplated, as will be explained subsequently.

Briefly, this invention involves the adaptation of a complexing orchelating agent for color-forming metal salts such that the complexingagent is suitable for combination with a cosolvent for both thechelating agent and the color-forming metal salt and is preferably alsosuitable for combination with other ingredients comlmonly used inletterpress, dry offset, wet offset, rubber plate, and flexographicinks, or the like; whereby the complexing agent serves as a desenstizingagent for carbonless paper, action paper, carbonless manifold copysheets, selfcontained copy sheets, and similar applications of dyeprecursor/coreactant chemistry. The desensitizing (complexing) agentshould be capable of forming a chemical complex or chelate with acolor-forming metal salt whereby the chelate or complex is (a)substantially colorless, white, or of a color which strongly contrastswith purple or black, and is (b) more stable, in oleaginous or otherorganic media, than a DTO/metal salt complex. The -preferreddesensitizing agents of this invention also desensitize the electronacceptor which forms a color by interaction with a leuco dye or similarelectron donor. Tile adaptation of the preferred desensitizing agentsfor use in this invention has also resulted in desensiiizingcompositions which satisfy the toxicity, solubility, dermatologicalactivity, and color Criteria described previously. Preferably, thedesensitizing compositions are formulated so as to be non-hygroscopic.The preferred desensitizing agents suitable for use in the preferreddesensitizing compositions are the partial esters of EDTA(ethylenediaminetetraacetic acid) and various analogs and homologsthereof. These preferred agents are effective desensitizers forreactions between a DTO-type dye precursor (eg. DTO, DBDTO, yDOEDTO,etc.) and the conventionally used coreactant neavy metal salts, eg. thesoaps of nickel, copper, cobalt, or, less preferably, cadmium. Theseagents also desensitize the electron acceptors which produce a strongcolor upon interaction with leuco dyes or the like. Other organicpolycarboxylic acid and/or polyalcohol derivatives, e.g. derivatives ofcitric or tartaric acid or the like, and nitriloacetic acid, have manyof the desirable properties of the EDTA esters but are ordinarily tooweak in their chelating effect to satisfy the criteria of thisinvention. This relatively low chelating or desensitizing effect also isapparent for lauric acid, oleic acid, cod liver oil, etc. Three otherclasses of organic compounds have marginal utility in this invention,but are not preferred: (1) polyamines wherein at least one amino groupis substituted on a carbon atom which is beta or gamma to a secondary ortertiary nitrogen, (2) compounds containing two adjacent carbonylsand/or oxime radicals, i.e. R-(CO)-(CO)-R, R(CO)-(C=NOH)-R', or

(where R and R are organic radicals), and (3) vicinal dimercaptans. Thecompounds of classes (1) and (3) tend to be toxic or dermatologicallyactive or hygroscopic. The compounds of class (2) are more suitable, buttend to produce yellowor pink-colored complexes, some of which do notprovide the high contrast background of the substantially white orsubstantially colorless EDTA-ester/ metal salt complexes. The preferreddesensitizing agents of this invention are useful in a wide variety ofprinting inks and thus can provide production quantities of partiallydesensitized carbonless or action paper, carbonless manifold-stylebusiness rforms, or the like. These agents can also be dissolved inhighly volatile cosolvents (as described previously), thus forming adesensitizing composition useful for the self-contained type ofcarbonless or action paper (see the aforementioned Matson patent).

The invention and its application to manifold-style business forms andself-contained carbonless or action paper (i.e. the self-marking paperof Example 18 of U.S. patent to Matson, No. 3,516,846) can best beunderstood by referring to the drawing, wherein lFIG. l is a perspectiveview of a manifold-style business form -printed and used according tothe present invention, and

FIG. 2 is a side elevational view illustrating a means and method fordesensitizing self-marking paper, the selfmarking paper being shown incross-section and greatly enlarged in thickness.

IReferring to the drawings, FIG. 1 shows a manifoldstyle business form11 containing an original or top sheet and two copy sheets. As isconventional in the art, the top sheet is coated, on its reverse surfaceonly, with a layer 13 of encapsulated dye precursor, in this Vcase amicroencapsulated DTO-type compound, specifically N,Nbis(dibenzyl)dithiooxamide. As is conventional in carbonless paper utilizing DTO-typedye precursors, a colsolvent capable of dissolving both the DTOderivative and a coreactant metal salt is also encapsulated and includedWithin layer 13. The lirst copy sheet has a similar coating 23 on itsreverse surface. The obverse surfaces 25 and 27 of the second and thirdcopy sheets, respectively, are coated with nickel rosinate, which, uponrupture of microcapsules in the coating 13 or 23 reacts with the DTOderivative and cosolvent physically liberated thereby and forms purpleor blue-black images. The microcapsules in layer 13 or 23 are rupturedby the pressure of the ballpoint pen or pencil used to enter the data inthe various columns of the original or top sheet of manifold form 11. lAsignificant feature of manifold form 11 is that it contains provisionfor two columns of numerical data, these columns being designated on thetop sheet of form 11 by reference numerals 15 and 19, and of these, theinformation in column 19 is intended to be confidential. Accordingly,the first copy sheet contains a desensitizing layer 17 which preventsimages (corresponding to the numerical data in column 19) from beingformed only in the area corresponding to column 19 of the top sheet;hence, the data of column 1S do appear on this first copy sheet. Thesecond copy sheet, which is intended to be an exact duplicate of theoriginal or top sheet, is not provided with the desensitizing layer;therefore, all the data entered on the original in ball point pen orpencil do appear, including the data of column 19. In manifold form 11,layer 17 has been provided by running the rst copy sheet through aletterpress inked with the trimethylester of ethylenediaminetetraaceticacid (EDTA), the EDTA ester being dissolved in dibutylphthalate (DBP)and mixed with a suitable ink base. The blocked out area covered bylayer 17 is printed in proper register with the area corresponding tocolumn 19 by conventional multi-station printing techniques. (Thesetechniques ensure that layer 17' will not overlap column 15 of the firstcopy sheet.)

In an alternative embodiment of FIG. 1, coatings 13 and 23 comprise amicroencapsulated electron-donating dye precursor such as a leuco dye,and the coatings on obverse surfaces 25 and 27 comprise anelectron-acceptor, such as attapulgite clay; see U.S. Pat. 2,777,780,cited previously. In this leuco dye embodiment, layer 17 is,nevertheless, comprised of the same EDTA tri-ester and is provided inthe same manner.

In FIG. 2, a self-marking paper sheet 31 made according to Example 18 ofU.S. Pat. 3,516,846, containing the encapsulated DTO derivative andencapsulated cosolvents 35, and further containing nickel rosinatedistributed throughout the thickness of the sheet, is shown beingdesensitized with a brush applicator 39 containing, in reservoir 41(shown in phantom), the trimethylester of EDTA dissolved in ethylalcohol, i.e. the desensitizing composition 43. The desensitizingcomposition 43 ows onto the surface of paper 31 through the brush 33 andpenetrates deeply into and through paper 31. As a result of thispenetration, the nickel rosinate is rendered inactive or desensitized.However, the ethyl alcohol in the desensitizing composition 43evaporates rapidly, and the already-recorded information, represented byimage 37, is not substantially affected by the desensitizing treatment.In one form of the embodiment shown in FIG. 2, the applicator 39 is setup as an after-treatment station for the printout from a computer,thereby rendering tamperproof the print-out information 37 on theself-marking paper 31. As is readily apparent to those skilled in theart, the desensitizing method of FIG. 2 can also be applied to the copysheets in manifold form 11 of FIG. l.

f The preferred practice of this invention involves the use in printinginks or the like, of desensitizing agents capable of chelating metals inmetal salts such as MzZm, where M is nickel, cobalt, copper or the like,Z is a suitable organic or inorganic (eg. Clr, B1", NO3, SOE, etc.)anion, z is the valence of Z and m is the valence of M. Examples ofsuitable organic anions are the anions of C1-C24 aliphatic andcycloaliphatic carboxylic acids, including the rosin acids (e.g. abieticacid) and saturated and unsaturated fatty acids.

The preferred desensitizing agents are compounds of the formula:

wherein X is a divalent aliphatic or cycloaliphatic radical, preferablyan alkylene radical of the formula or a cyclic radical, such ascyclopentane, cyclohexane, etc., wherein the nitrogens are substituted1,2- or 1,3;

A, B, C, and D are selected from thefollowing group of substituents:

hydrogen, an aliphatic or cycloaliphatic group,

CH2-COOH 1 CH2COOR 1 (where R is aliphatic, preferably a lower alkylgroup such as methyl, ethyl, propyl, isopropyl, or butyl, optimumresults being obtained with methyl), and

XNF

where X' is similar to X, E and F are similar to A, B, C, and D; E or Fcan therefore be another -X--N(E) (F) unit, such that structures of thefollowing type are formed:

N--\XN/ X-N\ B/ F where a is O, 1, 2, 3, 4, or other small integer.

For convenience, the compound (HOOCCH2) ZNCHZCHZN (CHZCOOH) 2 has beenreferred to as ethylenediaminetetraacetic acid (EDTA), its common name.It is to be understood that this is the same compound indexed byChemical Abstracts under the name (ethylenedinitrilo)tetraacetic acid.Throughout this specification, the common nomenclature is used, both forEDTA and its homologs and analogs.

As pointed out previously, other -COOH, -COOR, and/ or OH-containingcompounds are marginally operative, but not preferred for use in thisinvention, examples being derivatives of tartaric acid, citric acid,nitrilotriacetic acid, and the like which are soluble in non-aqueousmedia. It is an essential feature of this invention that thedesensitizing agent be capable of forming a chemical complex (i.e.coordination compound with chelate-like stability) with coreactant metalsalts such that'this complex has at least as much stability as complexesof DTO or derivatives thereof with these same coreactant metal salts.The metal salts which are suitable for practical commercial use, e.g.cobalt, nickel, and copper, form very stable colored complexes with DTOor its derivatives in the following order of stability (least togreatest): DTO/Co, DTO/Ni, DTO/Cu. Since nickel is so typical in itsbehavior, the magnitude of the stability of the DTO/ Ni complex canserve as a reference point for the essential requirements of thisinvention. (The color-reactive DTO derivati-ves with dye precursorutility, e.g. the N,N'diorgano-substituted DTO derivatives, behave in amanner which is chemically analogous to DTO itself; these derivativesvary primarily as to their solubility characteristics, their vaporpressure, and the color of the complexes they form with a given metal.)Throughout this specification, the term DTO, DTO-type compound, or DTOderivative is used to describe dithiooxamide itself and itscolor-reactive derivatives with dye precursor utility, particularly theN,Ndiorgano-DTO derivatives.

To provide an approximate indicator for the degree of metal chelatestability required for organic media, reference is made to a body ofchemical literature consisting of studies in aqueous media, which havedeveloped the basic lEach of these groups must be present as at leastone, but not all, of A, B, C, and D.

mathematics used in measuring stability constants for coordinationcompounds, chelates, and similar chemical complexes and compoundscontaining metals.

The stability constants for the step-Wise additions of ligands (K1, K2,etc.), e.g. protonated ligands, and the cumulative or gross addition ofligands are dened in a publication of the Chemical Society (London)entitled Stability Constants, published in 1956. See particularly pagesxii-xix of this'publication. A further discussion of these stabilityconstants, including tabulated log K or log K1, log K2, etc. values andlog values, can be found in an Introduction to Coordination Chemistry,second ed., by D. P. Graddon, Pergamon Press, 1968. Although thesestability constant values are for aqueous media, it has been lfound thatif, for a particular chelate, the log K (log K1, log K2, etc.) valuesare in excess of about 9 (preferably at least l1), there is someassurance that the nickel (or copper or cobalt) chelate will be stablein oleaginous or other organic media, even in the presence of a DTO-type compound. Stated another way, it has been found that citric andtartaric acids, known chelating agents for nickel, suitably modified forsolubility in organic media, are marginally operative in this invention.Therefore, a suitable desensitizing ink for commercial practice shouldcontain a complexing or a chelating agent (i.e. desensitizing agent)which forms a complex with nickel ions that is more stable than thoseformed by citric or tartaric acids in such organic media.

Three classes of compounds, in addition to the l -N-CHa C O 0H type,have sufficiently strong chelating ability to be used in this invention,but are much less preferred due to toxicity, dermatological activity,hygroscopic effects, unsatisfactory color-forming effects (bright pink,dark brown, etc.), orrother undesirable properties. These are:

(1) Polyamines wherein at the least one amino group is substituted on acarbon atom which is beta or gamma to a secondary or tertiary nitrogen,e.g. compounds of the formula where R, R', R, and R'" are hydrogen or asuitable aliphatic or cycloaliphatic group;

Q is a suitable organic radical,

a and c are 2 or 3, and

b is 0, 1, 2, 3 l0, provided, that if b=0, at-l-c is 2 or (2) Compoundscontaining two adjacent carbonyls and/ or Oxime radicals, i.e.R-(CO)(CO)-R',

or R(C=NOH)(C=NOH)R where R and R are suitable organic radicals such asaliphatic, cycloaliphatic, or aromatic groups, and

(3) Vicinal dimercaptans, i.e., HS-R--SH, where R iS a 1,2-disubstitutedaliphatic, cycloaliphatic, or aromatic group.

Of these three classes, class (2) has the least disadvantages.

Broadly speaking, this invention has these aspects:

`First, a desensitizing composition for carbonless paper (which could bein the form of a letterpress, rubber plate, dry offset, lithographie, orflexographic ink-like material or other ink material suitable for largeand small printing runs); second, printed carbonless paper forms (suchas form 11 of FIG. 1) which have been at least partially desensitizedduring the printing run; and, third, a method of desensitizingself-contained, self-making carbonless paper, as shown in FIG. 2.

The desensitizing composition, to be practical, should contain acosolvent, i.e. an organic liquid capable of serving as a solvent andreaction medium for the desensitizing agent and the coreactant metalsalt, e.g. the nickel, copper, or cobalt soap. These desenstizingcompositions are of three basic types: (a) ink-like materials suitablefor letterpress, rubber plates, and dry offset printing, (b) materialssimilar to (a) but suitably modified for lithographie or wet offset, (c)materials similar t (a) or (b), but suitably modied for flexographic use(e.g. containing volatile vehicles boiling at less than 125 C.; examplesof such vehicles are ethanol and mixtures of ethanol and Water). Ethanolcan also serve as the cosolvent, as can methanol, propanol, and otheralcohols, cyclohexane, acetone, acetonitrile, nitromethane, and thelike. The type (c) compositions can be modified for use in theafore-mentioned method which is described in FIG. 2.

In compositions of types (a) and (b), the Cosolvent is preferably anester-type plasticizer, e.g. the dialkyl esters of phthalic acid (suchas dibutyl phthalate); organic esters of phosphoric acid, e.g. trialkylphosphates (such as tributyl phosphate or trioctylphosphate) andtributoxyethylphosphate; esters 4and/ or ether derivatives of diethyleneglycol (c g. Carbitol acetate, Methyl Cellosolve, etc.); and compoundsof the formula RCOOR, where R and R are aliphatic or cycloaliphatic,e.g. butyl acetate, rosin acid esters, propyl propionate, etc.Furthermore, in these compositions, lan ink binder or viscositymodifying agent isnormally used. Common examples are the drying oils(tung oil, etc.). Particulate synthetic resins (c g. the polyurethanescommonly used in the art), and rosin acid esters can also serve thisfunction; all of these tend to set to an insoluble substance upon dryingor curing of the ink. It is common practice to include accelerators,e.g. driers, to facilitate curing of the drying oils. Metal salt driersare permissible, but less preferred in this invention. Silicones,mineral oil, and the like are also used to modify viscosity, but do notset in this manner. When an ink vehicle is included in addition to thepreviously described components, the vehicle should be of low volatilityin compositions of type (a) and (b) and of high volatility in type (c).In types (a) and (b), the usual oleaginous vehicles can be used, e.g.high boiling hydrocarbon oils.

As is conventional in the art, suitable pigments and fillers can beadded to the desensitizing ink compositions, e.g. carbon black, titaniumdioxide, and other commonly used pigments and fillers.

In compositions of type (c), synthetic resin binders are preferred andsuitable types of viscosity modifiers can also be added, as can theaforementioned pigments and fillers. It is to be noted that, althoughthe vehicle and Cosolvent in the type (c) compositions could be the sameorganic liquid, it is also permissible to add ester-type plasticizers toflexographic ink compositions.

Typical examples of desensitizing compounds of the polyamine,di-carbonyl or -oxime, and dimercaptan types described previously arecommercially available, e.g. triethylenetetraamine,tetramethylethylenediamine, dimethylglyoxime, and 1,2 dimercaptoethane.The compound EDTA is also readily available, and its partial esters canbe synthesized from EDTA and alcohols by techmques described in U.S.Pat. 2,428,353, cited previously. Alternatively, the EDTA or otherpolycarboxylic acid compounds can be fully esteried and then partiallysaponied by an appropriate number of equivalents of an alkali metalhydroxide. These esterilications techniques can also be used to makepartial esters of polycarboxylic acid analogs and homologs of EDTA, e.g.partial esters of trans-cyclohexane-1,2-diaminetetraacetic acid,diethylenetriaminepentaacetic acid, triethylenetetraamine-hexaaceticacid, and the like. The preferred degree of esteriiication is C-l or C-2ester groups, where C is the number of carboxyl radicals in thepolycarboxylic acid precursor. The preferred esterifying agents arealkanols, e.g. lower lakanols, such as meth- 10 anol, ethanol, propanol,butanol, etc. Mixed esters (c g. methyl-ethyl, ethyl-butyl, etc.) can beprovided -by conventional ester interchange reactions.

Desensitizing compositions can be made up for use in this invention bycombining 3-99 percent by weight of desensitizing agent with l97 percentby weight of cosolvent and 0-96 percent by weight of one or moreingredients from a suitable conventional ink base (eg. tung oil,

accelerators, silicone oils, liquid hydrocarbon vehicles, and rosinesters). More specifically desensitizing ink compositions can be made bycombining 3-60 percent by weight of desensitizing agent with 1-40percent by weight of cosolvent and 15-90 percent by weight of one ormore of the ingredients of the ink base.

The following non-limiting examples are illustrative of the invention.In these examples, all parts are by weight, unless otherwise indicated.

EXAMPLE A Ink base compositions The following ink base compositions wereselected for combination and evaluation with glyoxime, polyamine (havingappropriately located beta or gamma amino groups), and polycarboxylicacid (of the EDTA type) desensitizing agents:

(l) An air curing ink with no drier and no volatile solvent vehiclecontaining tung oil, methyl silicone oil, and a rosin ester,(Consolidated Printing Ink, Inc., Ink No. 58960).

(2) A solvent evaporating ink (Lawter Uroset B-2 of Lawter Chemicals,Inc.).

(3) A solvent evaporation ink containing titanium dioxide (ConsolidatedPrinting Ink No. 57242C).

(4) A press-ready, air drying clear overprint varnish, with drier(Lawter ALVCO 2620W).

(5) A lithographic, air curing clear varnish with drier (Lawter Halex, aregistered trademark).

EXAMPLE B Desentizing ink compositions for letterpress For experimentalletterpress printing runs, the following desensitizing compositions wereused:

Ingredient: Parts by weight Desensitizing agent 20-30 Cosolvent 5-20 Anink base of Types (1)-(5), supra 56-85 EXAMPLES I-V Experimentalprinting runs All experimental printing runs were made with a VandercookProof Press with light, medium, and heavy pipette application of ink(IPI pipette). The Vandercook Proof Press is a scaled-down version ofstandard letterpress equipment. The sheets printed with thedesensitizing ink were conventional nickel rosnate-coated receptorsheets [3M Brand Carbonless Paper, Type 200, CF (coated `front) sheet].After the proof press run, a conventional donor sheet coated on itsreverse surface with encapsulated DBDTO and solvent, .e. a 3M BrandCarbonless Paper, Type 200 CB (coated back) sheet, was superimposed onthe treated CF receptor sheet and typed on in the usual manner. 'Ihetyping was done with CF sheets fresh from the proof press, as well as CFsheets which had been aged for at least a week. A sample printed CFsheet was considered effectively desensitized if an image failed toappear even a week or more after the 1'1 typing or after acceleratedaging tests involving brief exposures to 100 C.

The results of the proof press trial runs for the desensitizing agentsdescribed previously in various ink compositions are summarized in thefollowing examples.

EXAM-PLE I Dioxime desensitizing agents The following composition:

Component: Percent by weight Desensitizing agent (dioxime) 10Tributylphosphate (TBP) 5 Ink base: (1), (2), or (3) 85 was tested withthe following results:

This modified composition produced substantially the same results withthe two di-oximes named previously.

EXAMPLE II Polyamine desensitizing agents The following composition wasused in this example:

Component: `Percent by weight Desensitizing agent (polyamine) 30Cosolyent (TBP or DBP) 5 Ink base: (1), (2), (3), (4), or (5) 65 Theresults were as follows:

Sol- Ink Desensitizing agent vent base Result-commentsTriethylenetetraamine TBP (1) Effective, but CF eventually turnedyellow. D-.. TBP (2) Eective, but CF turned brown. Do TBP (3) Do.5-ethyl5(4amino2faza DBP (4) Effective; CF sheet rebutyl)1,9dia1nino3,7mained substantially co1- diazanonanel orless.

0.1 DBP (5) Do. Tetramethylethylene- DBP (1) Do.

diamine.

l F. Lions et al., Inorg. Chem. 2 (3), p. 597 (1963).

EXAMPLE III Vic.dimercaptan desensitizer When wt. percent 2,3dimercaptopropanol-l was combined with 65 wt. percent of ink base (1),(4), or (5) and 5 wt. percent DBP, the resulting compositionseffectively desensitized the CF sheet, but turned its surface darkbrown. The unpleasant odor and toxicity of the dimercaptan are furtherdisadvantages.

l 2 EXAMPLE 1V EDTA partial esters and homologous and analogouscompounds The following were the EDTA-type partial esters tested:

Compound number Name IV-A Trimethyl ester, monoacid oftranscyclohexane-1,2

diamlne-N,N,N',N-tetraacetic acid.

IV-B Tetraethyl ester, monoacid of diethylenetriamine-N,N,NN,Npentaacetic acid.

IV-C Trimethyl ester, monoacid of EDTA.

The composition used, unless otherwise indicated, was as follows:

Component: Wt. percent Desensitizing agent 30 ICosolvent (DBP) 5 Inkbase (l), (2), or (3) 65 The results were as follows:

Desensitizing agent, Ink

Compound No. base Comments 1V-A (1) Etective; CF sheet remainedsubstantially colorless. (2) Do. (3) Do.

(1) Effective; CF sheet remained substantially colorless; Also eectivewith a standard clay-coated CF sheet and a leuca-dye CB sheet (NCRCarbonless Paper).

This composition was 24 wt. percent Compound IV-A, 20 wt. percent DBP,and 56 wt. percent ink base (1), instead of the 30/5/65 formulation usedfor the other runs.

Compound IV-C (the EDTA trimethyl ester) was tested with a wide varietyof cosolvents other than DBP, but in the same 30/5/65 formulationdescribed previously. All of the following cosolvents were found to besuitable:

Ethyleneglycolmonomethylether (Methyl Cellosolve,

trademark of Union Carbide Corp.)

Diethyleneglycolrnonoethylether acetate (Carbitol Acetate, trademark ofUnion Carbide Corp.)

Trimethyl phosphate, triethyl phosphate, tributyl phosphate, andtrioctyl phosphate Tributoxyethyl phosphate Tricresyl phosphate Dimethylphthalate, diethyl phthalate, dibutyl phthalate,

and dioctylphthalate.

EXAMPLE V Marginally effective desensitizing agents Thirty percent byweight of the compounds to be tested were combined with 5 wt. percent ofcosolvent and 65 wt. percent of the base ink. The results of the trialruns were:

Base Eec- Compound Solvent ink tiveness Citric acid l/.[ghyl Cellosolve(see Ex. (1) Fair. Dodn (2) Poor. Do do (3) Do. Tartaric acid do... (1)Fair. Do .-..do--. (2) Poor. Do o (3) Do. N itrilotriacetic acidTributoxyethyl phosphate (1) Fair. Do 1 dn (2) Poor. Do do (3) Do.

Although these marginally active materials were not particularlydesirable for use in printing runs, they were adequate, as solutions inethanol, for desensitizing selfcontained, self-marking paper inaccordance with the method illustrated in FIG. 2 of the drawing.Apparently the mass action effect can be utilized in this method.Accordingly, desensitizing agents With a log K or 10g K1 of about 9-12are particularly suited to the method of FIG. 2.

EXAMPLE VI Flexographic inks It was found that the desensitizing agentsof the preceding examples could be used in exographic inks. Preferredilexographic inks comprised a water-ethanol solvent medium serving asvehicle and cosolvent, a particulate synthetic resin binder, and thedesensitizing agents. Other suitable cosolvents which could be includedin the solvent medium were: dialkyl sulfones and dialkyl sulfoxides,e.g. dimethylsulfoxide; aliphatic, cycloaliphatic and aromatic nitriles,e.g. acetonitrile, benzonitrile, etc.; aliphatic nitro compounds, e.g.nitromethane; ketones of the formula CH3-CO-R, where R is an aliphatic,cycloaliphatic, or aromatic group; amides of the formula R2CONR2', whereR and R are hydrogen or an aliphatic group, e.g. dimethylformamide,dimethylacetamide, etc.; liquid alkanols; and phosphoric acid amides ofthe formula (R2N)3PO, where R is hydrogen or aliphatic.

Those liquids in the above list which boil at less than 125 C. can beused as vehicles as well as cosolvents, but higher boiling liquidspreferably are present in minor amounts as cosolvents for the metal saltand DTO compound.

What is claimed is:

1. A composition comprising:

(1) 3-99% by weight of a complexing agent soluble in organic media andcapable of forming a coordination compound with a metal salt, said metalsalt being color-reactive with dye precursors, and wherein saidcomplexing agent is capable of forming a complex in said organic mediawith coreactant metal salts such that said complex is more stable thancomplexes of dithooxamide or derivatives thereof with said coreactantmetal salts,

(2) 1-97% by weight of an organic liquid solvent capable of at leastpartially dissolving said complexing agent and said metal salt, saidorganic solvent being capable of serving as the organic medium for acoordination reaction between said complexing agent and said metal salt,and

(3) 0-96% by weight of a binder or viscosity modifying agent capable ofimparting a viscosity to said composition which is suitable for use in aprinting method.

2. A composition according to claim 1 wherein said complexing agent is acompound of the formula wherein X is a divalent aliphatic orcycloaliphatic radical, and A, B, C, and D are selected from the groupconsisting of:

hydrogen,

an aliphatic group,

a cycloaliphatic group,

-CH2COOH,

CHZCOOR, wherein R is aliphatic, and

wherein X' is similar to X, and E and F are similar to A, B, C, and D,at least one of A, B, C, D, E, and F being CH2COOH, and at least one ofA, B, C, D, E and F being CH2COOR, wherein R is as defined previously.

3. A composition according to claim 2 wherein said organic liquidsolvent is capable of dissolving dithiooxamide or a derivative thereofand a soap of nickel, copper, cobalt, or cadmium, and

14 said binder or viscosity modifying agent is selected from the groupconsisting of a drying oil, a silicone oil, a particulate syntheticresin, and a rosin acid ester. 4. A composition according to claim 3wherein said organic liquid solvent is an ester-type plasticizerselected from the group consisting of:

(a) dialkyl esters of phthalic acid, (b) trialkyl esters of phosphoricacid, (c) ester derivatives of diethylene glycol, and (d) compounds ofthe formula wherein R and R are aliphatic or cycloaliphatic, and saidcomposition further contains a hydrocarbon vehicle.

5. A composition according to claim 3 wherein said organic liquidsolvent comprises a vehicle which boils at less than C. and said binderis a particulate synthetic resin.

6. A composition according to claim 5 wherein said vehicle comprises alower alkanol.

7. A composition according to claim 1 wherein said complexing agent is acompound of the formula where R and R' are aliphatic or cycloaliphaticradicals. 8. A composition for desensitizing carbonless papercomprising:

(l) 3-60% by weight of a complexing agent of the formula wherein X isselected from the group consisting of CH2CHr-, -CH2CH2CH2, and1,2-trans-cyclo hexane, and A, B, C, and D are selected from the groupconsisting of -CH2COOH,

-CH2COOR, where R is lower alkyl, and

where E and F are similar to A, B, C, and D, at least one of A, B, C, D,E, and F being -CHZCOOH and at least one of A, B, C, D, E and F being-CH2COOR, where R is lower alkyl, (2) 1-40% by weight of an ester-typeplasticizer selected from the group consisting of:

(a) dialkyl esters of phthalic acid,

(b) trialkyl esters of phosphoric acid,

(c) ester derivatives of diethylene glycol, and

(d) compounds of the formula wherein R and R' are aliphatic orcycloaliphatic, said plasticizer being capable of at least partiallydissolving said complexing agent and providing a medium for the reactionof said complexing agent with a soap of nickel, copper, cobalt, orcadmium, and

15 (3) 15-90% by weight of a viscosity modier or ink binder selectedfrom the group consisting of a drying oil, a silicone oil, a rosinester, and a particulate synthetic resin.

References Cited UNITED STATES PATENTS 3,262,386 7/1966 Gordon 117-3613,364,052 1/1968 Martino 117-362 3,516,846

1 6 OTHER REFERENCES ALLAN LIEBERMAN, Primary Examiner U.S. C1. X.R.

10G-236, 237, 240, 264, 287 =SB; 26o- 30:6 R, 31.4 R,

6/19'70 Matson 117-36.2 10 31.8 G, 31.8 R,'32.2, 33.2 R, 33.4 R, 33.6UB, 33.16 R

